Sponsored by: LMD Aluminum Committee
Program Organizer: Julian V. Copenhaver, Technical/Quality Manager, NSA A Division of Southwire, P O Box 500, Hawesville, KY 42348
Wednesday, AM Room: A10
February 7, 1996 Location: Anaheim Convention Center
Session Chairperson: Dr. Madhu Nilmani, University of Melbourne, Department of Chemical Engineering, Parkville, Victoria 3052, Australia
MODELING THE FEEDING OF ALUMINUM ALLOY CASTINGS: Alauddin Ahmed, Dr. D. Apelian, Worcester Polytechnic Institute, Aluminum Casting Research Laboratory, 100 Institute Road, Worcester, MA 01609; A. K. Dahle, Dr. Lars Arnberg, The Norwegian Institute of Technology, Department of Metallurgy, N-7034, Trondheim, Norway
Aluminum alloy castings, in general solidify with the growth of equiaxed dendrites followed by eutectic precipitation. Dendrite growth and eutectic precipitation are influenced by a complex combination of macroscopic transport phenomena and microscopic solidification kinetics. The feeding process, i.e. the shrinkage driven material transport and solidification mechanism are critically dependent on the local solid fraction. Consequently, it is necessary and possible to divide the mushy zone into several distinct regions in order to successfully model the solidification and feeding process. These regions have different mechanical and solidification characteristics and are governed by different transport mechanism and solidification kinetics. A mathematical model for solidification and feeding is developed coupling the macroscopic transport process and microscopic solidification kinetics taking into account the various regions of the mushy zone. A finite element computer program is developed to solve the model and predict several important solidification variables such as dendritic coherency, grain size distribution, feeding and shrinkage. The phenomenology of feeding castings and pertinent results of the model will be reviewed.
MODELLING OF ELECTROMAGNETIC PHENOMENA IN A MASSIVELY PARALLEL PROCESSOR COMPUTING ENVIRONMENT: Dan P. Cook, Reynolds Metals Company, Corporate Research & Development, 4th and Canal Streets, Richmond, VA 23261; Dr. D. MacKay, Intel Corporation, Super Computer Divisions, Oak Ridge National Lab, Building 4500N, Room I114, Oak Ridge, TN 37831-6203
A computer model which calculates the electromagnetic phenomena in electromagnetic casting has been ported to the Intel Paragon, a distributed memory, massively parallel processor (MPP) supercomputer. A parametric study of the mesh density requirements was carried out over a wide range of current frequencies and electrical conductivities. These results were validated by several analytic solutions of the vector potential form of the induction equation. Finally, a study was conducted to determine the optimum number of processors to use for the computations for any given problem size.
INSTABILITY OF A LIQUID METAL SURFACE IN AN ELECTROMAGNETIC FIELD AND RELEVANCE TO EMC: Ryuichi Kageyama, Graduate Student, Dr. J. W. Evans, Professor of Metallurgy, Department of Materials Science and Mineral Engineering, University of California, 577 Evans Hall # 1760, Berkeley, CA 94720-1760
In electromagnetic casting (EMC) the surface of the molten metal, at the solidification front around the periphery of the melt pool, is not confined by a solid mold (as in, say, direct chill casting) but is free to move. Consequently, disturbances of the melt surface are reflected in defects (waviness) in the solid ingot. The present paper examines the dynamics of a liquid metal surface in an electromagnetic field comparable to that of EMC. Numerical calculations of the flow of metal and motion of the melt surface have been accompanied by laboratory experiments in which a laser vibrometer has been used to measure the oscillations of the free surface of a mercury pool. Surface oscillations grow with increasing electromagnetic field strength in both the computations and the experiment, probably originating from the turbulent flow in the melt. The implications for EMC are discussed.
THERMO-MECHANICAL MODELLING OF THE 3C ROLL CASTING OF ALLOYS: Phillippe Jarry, Senior Scientist, Denis Toitot, Pierre-Yves Menet, Pechiney Centre de Recherches de Voreppe, BP 27, F-38340 Voreppe, France
In the roll casting process, coupling between the thermokinetics of solidification and mechanics of deformation is governed by the rolling operation. This is the basic principle of a numerical simulation of the 3C process based on the two-dimensional large deformation dedicated FORGE2 program. Heat transfer coefficients are calculated from the contact pressure, which is itself calculated from the temperature field; this causal loop governs the convergence of the computation. The model provides both global results in terms of rolling force, exit temperature, etc..., and local mappings of relevant variables within the roll gap; it allows predictive computation of different casting configurations (including down gauging) as well as it helps the metallurgical understanding of microstructure and defect formation.
SIMULATING AND OPTIMIZING AN Al-SiC COMPOSITE MIXING TANK: D. Kocaefe, Rung T. Bui, Département des sciences appliquées, Université du Québec à Chicoutimi, 555, boulevard de l'Université, Chicoutimi, Québec, Canada G7H 2B1; R. Provencher, T. Bourgeois, Alcan International Limited, P. O. Box 1250, Jonquiére, Québec, Canada G7H 4K8
Quality of SiC reinforced aluminum composites depends on the uniformity of the particles in the matrix which in turn is defined by the good mixing conditions in the holding furnace. A 3D, two-phase model is developed to simulate the mixing of Al-SiC mixtures in a holding tank which has a shape of truncated cone and equipped with an off-center mixer. The objective is to evaluate the mixing process using various operational and design parameters and to determine the conditions that will give the best mixture in terms of homogeneity. Due to complex geometry, the commercial code FLOW3D(TM) which has a multi-block option was used for this model. An optimization study is carried out by changing the various design and operational parameters such as the shape and dimensions of the mixing tank, impeller dimension, rotational speed, cone angle and melt height. It was observed that the mixture becomes more uniform with increasing impeller diameter, rotational speed, and decreasing melt height and cone angles. However, a certain increase in angle might be preferable. Even though this results in a slight decrease in homogeneity of the system, there is a significant augmentation in heat transfer efficiency due to the increase (as much as 30%) in the top surface area of the cone.
10:10 am BREAK
SOLUTE REDISTRIBUTION DURING STEADY STATE DIRECTIONAL SOLIDIFICATION OF A TERNARY ALUMINUM-BASE ALLOY: M. Chen, Dr. T. Z. Kattamis, Dr. H. D. Brody, Department of Metallurgy, University of Connecticut, 97 No. Eagleville Road, U-136, Storrs, CT 06269-3136
Several dendritic monocrystals of Al-3.75%Cu-1.5%Mn were directionally solidified at various growth rates under a constant thermal gradient of 6.8x103 K/m. Solidification was interrupted at a given time by quenching the remaining liquid. Copper distribution profiles within the dendrites and the surrounding liquid were determined in transverse sections corresponding to various temperatures at the moment of quench and were compared with computed predictions of a solute redistribution model. Copper concentration monotonically increased with increasing fraction solid and decreasing temperature. Manganese concentration first increased with increasing fraction solid, reached a plateau and subsequently decreased. Below the ternary eutectic temperature copper concentration at a given fraction solid decreased with increasing growth rate. Measured solute concentrations agree reasonably well with computed predictions.
A STUDY OF THE EFFECT OF COOLING DIRECTION ON THE MACRO SEGREGATION OF A BINARY METAL ALLOY DURING SOLIDIFICATION: Xianxi Jin, Dr. Will Schreiber, The University of Alabama, Department of Mechanical Engineering, P. O. Box 870276, Tuscaloosa, AL 35487-0276
The effect of solidification direction on buoyancy-induced convection in a binary alloy and the resulting concentration macro segregation are numerically simulated in a three-dimensional rectangular cavity. The system of equations governing the transport of momentum, heat, and species is based on the modified continuum transport equation and is solved using the SIMPLE computational scheme with a multi-grid method to solve the pressure correction equation. The freezing of Al7%Si is simulated and results are discussed. The temperature, concentration, and velocity fields during solidification and, consequently, the distribution of solute in the solid, are found to be strongly affected by the solidification direction.
INVESTIGATION OF RAPID MOLD HEATING AND COOLING TECHNIQUES TO OPTIMIZE PART QUALITY AND CYCLE THROUGHPUT: Mary-Jo Matthews, Makhlouf Makhlouf, Aluminum Casting Research Laboratory, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609-2280
A continuous tilt pour casting process at an aluminum foundry was investigated, modeled, and simulated with a commercial solidification software package. In order to reduce the cycle time and optimize the quality of the chosen casting, several cooling channels were designed and modeled using the software. Due to enhanced temperature gradients in the cycle, an improvement in the quality of the casting is expected. One channel design that significantly reduced the cycle time, while maintaining or improving the quality of the part, was run under real manufacturing conditions. The mold was machined, and any other process changes were made to match the conditions stated in the simulation. The casting produced under the forced cooling conditions was then checked for quality by x-ray inspection.
DEVELOPMENT AND COMMERCIALIZATION OF A 3000 SERIES BODY STOCK ALLOY USING THE LAUNER BLOCK CASTER: Bill Newton, Manager, Technology Development, Golden Aluminum Company, 1600 Jackson Street, Golden, CO 80401
Paper will describe the development and commercialization of a 3000 series body stock using the Launer block caster located in San Antonio. Starting with a 5000 series alloy, 5349, and describing its entry into the can-making industry, and its differences from mainstream 3104/3004 alloys. The decision to change the alloy to one which was closer to the regular 3004/3104 alloys we use; the evolution of this alloy and its subsequent acceptance by the can makers.
MAGSIMAL-59, AN AlMgMnSi-TYPE SQUEEZE-CASTING ALLOY DESIGNED FOR TEMPER F: Ulrich Hielscher, Horst Sternau, Dr. Hubert Koch, Alois J. Franke, Aluminium Rheinfelden GmbH, P. O. Box 11 40, D-79601 Rheinfelden, Germany
To get high mechanical properties using standard squeeze casting alloys (for
example, A356), it is indispensable to make a heat treatment. That means
solution heat treatment and quenching and artificially aging. For this reason,
we were challenged to develop an alloy that provides sophisticated mechanical
properties without any heat treatment. Compared to A356 T6, values in brackets,
the new alloy has yield strength > 21 ksi [>32 ksi], tensile strengths
> 42 ksi [43 ksi], and elongation > 15% [10%] in temper F. Fatigue
strength (r=-1, high frequency pulsation test) is > +/- 16 ksa [13.5]. To
meet these properties, a casting process with high solidification velocity like
squeeze casting or high pressure die casting is necessary. Magsimal-59 is of
the AlMgSiMn-type. The microstructure consists of -Al and a very fine dispersed
ternary eutectic. The microstructure and the influence of cooling rate on the
mechanical properties will be discussed including some examples of castings.
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